This study proposes to study granulocyte colony stimulating factor (GCSF) as an early marker for bacterial infection since it appears to be valuable for this application in adults. Through this study we will recruit infants admitted to the Newborn Intensive Care Unit at the University of New Mexico Hospital who are being evaluated for bacterial infection and measure their GCSF levels. We will then determine which infants indeed have bacterial infection (through blood, cerebrospinal fluid, or urine culture results) and compare GCSF levels.